If looking for a self-contained 12 Volt LED fixture, I'd check RV stores like Camping World or local RV supply retailer.
Many new RVs have gone to LED lighting so they can provide more and improved lighting without discharging the house battery as quickly. Most look very easy to install and have a switch built into fixture.
Camping World lists different sizes and styles. One, for instance, produces 350 lumens at 0.22 AMP draw. If I were installing in my van for camping I would probably consider at least four fixtures to better distribute lighting and reduce shadows. If for detail work inside a van I'd probably add some directly over work surface too. If some are not needed they can always be turned off separately.